I'm glad to announce that yesterday the kwin-tiling branch was merged into kwin trunk by commit 1118677!. It will be available in KDE SC 4.5. Please keep in mind that it is an experimental feature with rough edges. Bug fixes are already on the way, but some things, like session saving and so on are absent. Please do add feature requests and bugs to the KDE bug tracker.
This screencast should show off a few things. Apparently xvidcap produced really bad video, so I will have to do it again, watch out for updates here.
Thanks to Martin Graesslin for being my mentor during Season of KDE, and all the others who bugged me with emails about when tiling would be integrated into KWin :)